Studies On Adaptive Single-phase Auto-reclosure Based On Wavelet Energy Spectrum Algorithm For EHV Transmission Lines

EHV transmission line faults are mostly single-phase ground fault, of which more than 80% of transient faults. Automatic reclosing technique is one of the measures to ensure security and stability of the power system. The reliability of electricity power and the stability of system can be improved greatly by auto-reclosing technology. However, the implementation of a permanent fault conditions reclosing not only will the power system is once again under the impact of short-circuit current, but also to make electrical equipment conditions to deteriorate. Although we can choose reclosing time and can improve impact of the stability of system, when the electricity power system was reclosed and the impact of the equipment of the reclosing of permanent fault is inevitable. Therefore, in order to avoid automatic reclosing on permanent fault overlap, we should determine the type of fault to achieve adaptive reclosing.This paper first analyzes the changing process of electric quantity when it appears transient single-phase fault or the permanent fault in EHV transmission lines. At the same time, combining domestic and foreign research results, the combustion characteristics of the primary arc, the secondary arc, and the arc extinction time, fault-phase recovery voltage after a fault such as a number of different changes in the transient and steady-state phase are further researched and analyzed.Meanwhile, according to fault arc characteristics on the impact of the fault phase voltage, a new algorithm of adaptive single-phase auto-reclosure of transmission lines based on wavelet energy spectrum research is proposed, which is using discrete wavelet analysis of high-frequency transient components, by comparing the difference in the energy spectrum of high-frequency components. Based on wavelet energy spectrum analysis, algorithm of single-pole adaptive reclosure scheme for transmission lines is proposed. On the basis of establishing primary and secondary arc models of transient fault and by use of DB5 discrete wavelet, the multi-resolution analysis on voltage signal of faulty bus is performed, and the spectrum energy of its high-frequency component within specified time window is calculated. When transient fault occurs, the spectrum energy of voltage is higher and exceeds the specified threshold during the six cycles after the trip out of circuit breaker, however these conditions are not satisfied while permanent fault occurs, thus these conditions can be taken as the criteria for fault identification. The correctness of the proposed method is verified by simulation results. This paper is comparing the bus voltage of fault phase energy spectrum of the transient component, which can be identified before the arc extinguishing. It is not interrupted by the transition resistance, fault location and other factors. Only in the implementation of instantaneous reclosure failure to prevent a permanent fault conditions coincide huge impact on the system. It is not only meeting the reliability, but also increasing the rapidity.The algorithm mentioned above is proved to be correct and effective by lots of simulations base on PSCAD, both in time and accuracy on the criteria presented in this paper to be superior to the traditional circuit breaker after a fault-based fault cannibalism pressure after tripping voltage criterion, the compensation voltage criterion, combined compensation voltage discrimination means. Its performance can also endure the influences of various factors, including fault distances, types, inception angles, fault path resistances of, and is reliable. This plan only need withdraw the PT two biographies changing the voltage signal, realizes simply, and it is advantageous in the actual field application.